Nitrite concentration control device for water base metalworking fluids

ABSTRACT

A DEVICE IS PROVIDED FOR DETERMINING NITRITE CONCENTRA- TION OF LIQUIDS BY SATURATING A CELLULOSE MATERIAL IMPREGNATED WITH POTASSIUM IODIDED AND STARCH WITH A SOLUTION OF A NON-VOLATILE ACID HAVING A PKA OF FROM ABOUT 2 TO ABOUT 5 AND A NON-VOLATILE REDUCTANT, AND DRYING THE CELLULOSIC MATERIAL THUS TREATED.

United States Patent Oflice.

3,826,620 Patented July 30, 1974 3,826,620 NITRITE CONCENTRATION CONTROL DEVICE FOR WATER BASE METALWORKENG FLUIDS Charles A. Simpson, Aston, Pa., and Robert H. Davis, Pitman, and Michael Sedlak, Woodbury, N.J., assignors to Mobil Oil Corporation No Drawing. Filed Oct. 6, 1972, Ser. No. 295,632 Int. Cl. GOln 31/22 US. Cl. 23-253 TP Claims ABSTRACT OF THE DISCLOSURE A device is provided for determining nitrite concentration of liquids by saturating a cellulosic material impregnated with potassium iodide and starch with a solution of a non-volatile acid having a pKa of from about 2 to about 5 and a non-volatile reductant, and drying the cellulosic material thus treated.

CROSS-REFERENCE TO RELATED APPLICATIONS None.

BACKGROUND OF THE INVENTION (1) Field of the Invention Methods and devices for specific determination of approximation of concentration of nitrite components present in various liquids are known to those skilled in the art. Such methods for concentration control include titration, measurement of refractive index, or colorimetric measurements.

The aforementioned facilities are often unavailable at the specific point of use. In this respect, it will be apparent that a properly devised test paper, or other cellulosic material, would permit an operator to test a nitrite containing liquid for determining the necessity of adding additional nitrite.

(2) Description of the Prior Art In the aforementioned respects, certain nitrite test papers are commercially available; however, these papers are not considered satisfactory inasmuch as they do not tend to respond under the basic pH conditions of the liquid, and, furthermore, if acidified, they are found to be too sensitive and exhibit a positive response to nitrite concentrations which are far too dilute to have any significance, for example, where nitrites are employed as rust inhibitors in various liquid media, such as metalworking fluids.

SUMMARY OF THE INVENTION In accordance with the present invention, the disadvantages of the aforementioned test methods and control devices have now been obviated, as more fully hereinafter described, by providing a nitrite concentration control device which affords an efficient, quickly visible, ascertainment of desired minimum nitrite concentration in liquid media. In this respect it is found, in accordance with the more specific aspects of the invention, that potassium iodide-starch papers can be impregnated with certain selected reagents and will turn blue-black, or purple, in liquid media only when certain minimum nitrite concentrations exist.

In general, the present invention provides a device for determining nitrite concentration of liquids by saturating a cellulosic material impregnated with potassium iodide and starch with a solution of a non volatile acid having a pKa of from about 2 to about 5 and a non-volatile reductant, and drying the cellulosic material thus treated.

In its more specific aspects, in manufacturing the nitrite control device, an aqueous solution containing from about 0.5 to about 5%, by weight, of starch is prepared. There is also prepared an aqueous solution containing from about 1 to about 10%, by weight, of potassium iodide. The cellulosic material, e.g. paper, is then saturated with a combination of the aforementioned solutions or, in any sequence, with each of the solutions, permitting each solution to dry before the cellulosic material is saturated with the other.

As hereinbefore indicated, in manufacturing the control device a solution of a non-volatile acid, having a pKa of from about 2 to about 5 in a suitable solvent is prepared. A typical example of such acid is tartaric acid. Other examples of such acids include: citric acid, malonic acid, glutaric acid, malic acid, succinic acid, and mandelic acid. Solvents such as acetone, methanol and other lowboiling alcohols, water and methyl ethyl ketone may be employed. The amount of acid employed for this purpose is, in general, at least 5%, by weight, of the solution. In addition to the solvent, the solution may also contain minor amounts of water.

As also hereinbefore described, in the manufacture of the control device there is employed a solution of a nonvolatile reductant. A typical example of this reductant is ascorbic acid. Other examples of these reductants include: thiourea, sulfanilamide and hydroxylamine. Suitable solvents include water, methanol and other low-boiling alcohols, acetone and methyl ethyl ketone. In general, for most purposes, the reductant is present in an amount of not more than about 10%, by weight, of the solution. After the aforementioned solutions of the non-volatile acid and the solution of the non-volatile reductant are prepared, the cellulosic material is then saturated with each solution separately or with a mixture of the solutions, and the thus-treated cellulosic material is permitted to dry.

In selecting the acid for preparing a solution thereof, or a solvent in the additional presence of water, as hereinbefore indicated, the acid should have a pKa of from about 2 to about 5. In this respect, the pKa should not be so low as to prevent reaction between the reductant and the nitrite.

Insofar as the reductant solution is concerned, the purpose of this material is to prevent a positive test with ineffective concentrations of nitrite. Thus, the reducing agent must be essentially non-volatile, readily soluble in water, and must be capable of reacting rapidly with nitrous acid to prevent oxidation of iodide to iodine with the nitrite content is low. In this respect, urea or aromatic amines have heretofore been employed for decomposing nitrite; however, urea has been found to react too slowly, while aromatic amines have been found to be unstable for many uses; the same shortcomings are true with respect to ferrous ion, which is also found to be too unstable. Ascorbic acid, for example, is found to exhibit improved stability and reacts with nitrite so as to prevent color formation when the nitrite is sufiiciently depleted.

DESCRIPTION OF SPECIFIC EMBODIMENTS The following examples and comparative results obtained will serve to illustrate the preparation of the novel test device of the present invention and its efficacy in providing a rapid and accurate means for determination of minimum nitrite concentration in liquid media. It will be understood, however, that it is not: intended that the invention be limited to the particular device illustrated or the specific method for its preparation. Various modifications thereof can be successfully employed, as will readily be apparent to those skilled in the art.

EXAMPLE 5 grams of d-tartaric acid were combined with ml. of acetone and the mixture was heated until all of the acid had been dissolved. The resulting solution was then cooled to room temperature, yielding a volume of about 95 ml. Thereafter, 180 mg. L(+)-ascorbic acid was dissolved in ml. water and immediately mixed with the above-prepared tartaric acid solution. A starch-iodide paper was saturated with the above-prepared combined acid solutions by dipping the paper into the combined solution for a few seconds. The paper was then permitted to dry at room temperature. The test paper thus prepared was then employed for determination of minimum nitrite concentration of a metalworking fluid which had the following composition, by weight: triethanolamine, 0.4%; carboxylic acids (C C 0.04%; boric acid 0.04%; sodium nitrite 0.04%; and the balance water.

Employing the above-mentioned metalworking fluid, a comparison of nitrite concentration was made with respect to the use of the test paper of the present invention compared with other standard prior art methods. The results obtained are shown in the following table:

2. The method of claim 1 in which the non-volatile acid is tartaric acid.

3. The method of claim 1 in which the non-volatile reductant is ascorbic acid.

4. The method of claim 1 in which the cellulosic material is first saturated with an aqueous solution containing from about 0.5 to about 5%, by weight, of starch.

5. The method of claim 1 in which the cellulosic material is first saturated with an aqueous solution containing from about 1 to about 10%, by weight, of potassium iodide.

6. The method of claim 1 in which the solution of the non-volatile acid comprises at least 5%, by weight of the acid.

7. The method of claim 1 in which the aqueous solution of the non-volatile reductant comprises not more than about 10%, by weight, of the reductant.

8. The method of claim 1 in which the cellulosic material comprises paper.

TABLE.COMPARISON OF NITRITE-DETE RMINING TESTS Test Analysis time Equipment required Results obtained Prior art methods:

Capsule 1 10 minutes Reagents, test tubes, Semi-quantitative.

colort wheel, calibration 0118i Permanganate titration. 15-30 minutes. 2 burets, standard Quantitative.

solutions.

Nitrite paper 3 5 minutes Acid plus some glassware Nitrite present or absent,

no estimate of concentration.

Starch-potassium 4 iodide 5 minutes .do Do.

aper. Present development: Test paper seconds 1 test paper Strong. solid blue of example.

(purple) =sufiieient nitrite.

No blue =insuilieient amount of nitrite.

1 Reagents supplied from a capsule to form color with nitrite as per Griess method.

1 Permanganate oxidation in neutral solution.

a Test paper based on Griess method: Sulfanilie acid and Z-naphthylamine. Does not respond to nitrite in alkaline metalworking fluids.

4 Does not respond to nitrite in alkaline metalworking fluids.

It will be noted from the foregoing comparison of nitrite-determining tests that the novel device of the present invention exhibits a marked superiority in affording a simple, rapid and accurate determination for minimum satisfactory nitrite concentration of liquid media. Although the present invention has been described with certain specific and preferred embodiments, for purposes of illustration, it will be understood that various modifications and adaptations thereof, which will be obvious to those skilled in the art, may be made without departing r 9. The method of claim 1 in which the cellulosic material comprises a starch-iodide paper soaked in a solution of ascorbic acid and tartaric acid.

10. A device prepared by the method of claim 1.

References Cited UNITED STATES PATENTS 3,712,853 1/1973 Rittersdorf et a1. 23253 TP FOREIGN PATENTS 125,817 1/ 1968 Czechoslovakia.

OTHER REFERENCES Paul et al.: J. of Chemical Education, v. 40(8), August 1963, pp. 417-418.

Chem. Abstr., v. 65, No. 144296 (1966).

JOSEPH SCOVRONEK, Primary Examiner T. W. HAGAN, Assistant Examiner US. Cl. X.R. 

